Improvement in hot-air engines



.0. STBYENS. HOT AIR ENGINE.

Patented Oct. 17, 1865.

UNITED STATES PATENT OFFICE.

COLLINS STEVENS, OF BOSTON, MASSACHUSETTS.

AIMPROVEMENT IN HOT-AIR ENGINES.

Specification forming part of Letters Patent No. 50,506, dated October 17, 1 865.

To (1I L 'whom it may concer-n:

Beit known that I, COLLINS STEVENS, of Boston, in the county of Suffolk and State of Massachusetts, have invented a new and Improved Hot-Air Engine; and I do declare that the following is a i'ull and exact description thereof, reference being had to the annexed drawings and letters of reference thereon.

The nature of my invention is, first, the means and devices for the introduction of cold air between two or more movable and connected surfaces, constructed and arranged in sucha manner that the bulk of air introduced shall be confined and shail not be materially increased or diminished between such surfaces, and so that the air may be heated between such surfaces before it is permitted to expand, and so that `the pressure of the air being heated shall operate equally and counterbalance in opposite directions upon said surfaces, s0 as to produce no effect while the heated air is confined, and then using the expansive force of said heated air for producing power and motion, substantially as hereinafter described.

-To enable others skilled -in the art to make and use my invention, I will proceed to describe an air-en gine made in accordance therewith.

Figure 1 of 'the drawings is a longitudinal section of the engine. Fig. 2 is a top view, (except the iiy-wheel and shaft.) Fig. 3 is an end viewu Figs. 2 and 3 are on one-half the scaleof- Fig. 1.

The machine may have four cylinders of. equal length, and all (except, perhaps, the cyl- ,inder'F F') are of equal diameter. These cylinders hereinafterwillbe desi gna-ted as marked in the drawings by the letters, respectively, A A', C C', D D', F F'.

The cylinder A A' has working air-tight therein a piston, G. This piston will divide the space within the cylinders into two variable portions, designated, as shown in the drawings, by the letters A and A', respectively. The piston H works air-tight in C C', dividing it into two variable portions, C and C', re'

spectively. The piston H' works air-tight in the cylinder D D', dividing it into two variable portions, D and D', respectively. The piston I works air-tight in F F', dividing the cylinder into two variable portions, F and F'.v

These letters will be respectively used to denote such spaces and pistons, as A will denote the space within A A on one side of the piston G; A', the space on the other side. The said cylinders are closed air tight at the ends, having proper stuffing-boxes, so that the piston-rods may work air-tight. Said pistons are all connected with the shaft L L by connecting piston-rods, sothat all the-pistons move together as one solid, and just the same as if all the cylinders had a common axis and all the pistons a common piston-rod.

. Opening from the open air into A and into A are orices a anda', having valves therein, allowing air to iiow freely into A and A', but preventing the exit of air therefrom. Opening-from` A andA' into the tubes c and c' are the orifices b b', having valves therein, allowing air to flow from A or A' into c or c', respectively, but preventing any flow from c or c' into A or A'. The pipes c and c are connected by the pipe c", and open intothe furnaces B B', within which the air `from A and A' is heated. Thepipesco' c have each there in a stop-cock, d d.' d", so that the air from A and A' may be conducted in to either orlboth of said furnaces B B', or shut off from either or both, so that one of the furnaces may be opened and fuel supplied without stopping tlie engine or relieving the pressure in the other. The furnaces are strong air-tight chambers, with a door in each for supplying fuel, air-tight when closed.

A system of pipes,ff' f", connect the furnaces B B with C' and D'. These pipes have close to the furnaces valves or stop-cocks therein, so operated as to prevent the return of air from the pipes ff' f" into either of the furnacesu The pipe f' opens into C', and f"into D'. At tbejunction of these pipes with f is the valve t, so arranged that when it is in one position the pipe f andf' is open andf" is closed. In its'other positionfand f" are open and j" closed, so that air may iiow from the furnaces first into C and then into D' alternately. This valve is automatically worke by the engine.

Connecting C and F are the pipes h and h', which pipes are always open and connected. Connecting D and F' are similar pipes, k k',

always open and connected. Opening into the pipes It h' and k 7c' from the open air are two orifices, s and s', having each a valve therein,

h h' and the escape-pipe u is open and con.

nected with the pipes h h', and in its other'po# sition the escape-pipe u will be closed 'and cut oli' from h It and the pipes h h' h" will all be vopen and connected, so thatv the spaces C, C', and F' will be connected. The pipes k k'have v similar pipes connected, the pipe k" connecting with D', and the other (the escape-pipe u') opening into the air. A similar valve, t", opcrates at the junction of pipes lek/,16", and u', operating similarly to the valve t', and these valves t t' are so automatically operated that when the pipes 'u and k" are open and connected, as before mentioned, u and h" are closed, and when u and lo" are closed u' and h" are open. The valves t t' t" are all worked automatically byarod connected with the shaft LL by a crank or eccentric working at right angles to the cranks M M M, so that the motion of this rod is greatest when the pistonrods move the least.' This rod is connected with the valves by a crank. The valves shown 1, gr', may be forked and so arranged withV respect to the rod that a pin or projection upon the rod, when it is moving in one direction, shall l push vone of the forks, w,one side, bringing the other over the rod. On the return vibration the 'forks' shall be `pushed aside and w brought 'over the rod again.. The motion may thus be given to the v'alve's when the pistons are near one end of the cylinder.

In addition to the vusual metal packing used in the cylinders of steam-engines, the inventor yuses packing-rings of soft and unctuous mineral substances-such as soapstone or plumbago-for lubricating the hot-air pistons.

The operation of the machine is as follows: In Fig. l'the pistons are represented as moyfA ing from the shaftL L, and the valves t t t" are all arranged for that purpose. Cold air is.

flowing into A through the orifice a.' The air in A', first being 'brought to a tension' equal to that in-the furnaces B B', then ows through the pipes4 c c' c'.' into the furnaces B B', and is there being heated. Heated air is flowing into D' from the furnaces through the pipes j. f".

At the beginning of the stroke, owing to the` difference of the tension ofthe air in A' and in the furnaces B B', considerable power will be exerted usefully on the piston H', C being exhausted. A fter the tensions become equal.

the pressures on G and H' in opposite directions balance and neutralize each other. .Air

from F 'and D is escaping through the pipes k, k', and u' in'to the air. Hot air introduced by the previous vibration into C' is flowing throughy the pipes h h' h" into C and F, and forcing the piston I' along.. 'The pressure on both sides of H beinggnearly equal, no eiect vis produced. The pressure of the expanding air upon I forces that piston, and with it all the others, along.' The pistonst having completed this stroke the valves t t' t." automatically change.4 Cold air flows into A' through a. 'Air' is first condensed, and then ilows through ccc" i'nto the furnaces, is there heated, and lowsfroin the furnaces through the pipes ff' into C. Air escapes from C and Fthrough the pipes'lt, h', and u.' Air is' expanding and flowing into F' and D from D' through the pipes 7c k k", and forces the piston I, and with it all the other pistons', toward,V L L." The pistons having reached the other ends of their cylinders, the valves t t' t" again change and the pistons return as atfirst. The vibratory motion is changed to circular by the cran-ks M M M of the piston-rods and of the shaft L L, and the motion is equalized by the fly-wheel upon said shaft. The shaft L L is supported upon pillars O O. The lire within is supplied as follows The stop-cock d of the pipe cis closed and the door e is'opened and fuel supplied to the furnace B. The stop-cock d is then re opened, the door having frst'been closed, and the stop-,cock d" is closed and the door is opened and fuel supplied to the other furnace, B'. The door is then closed and the stop-cock reopened.4 Closing the stop-cock d causes air from A to flow into one of the furnaces, air from A' into the other. Should not the air be suiciently heated so as to till the spaces Gand F or D and F' without becoming rarer than the air outside, air will iiow through the ori ices s or's' and prevent a prejudicial pressure upon the piston I. The arrangementof the details in the abovedescribed engine is made with special refer- -ence` to a clear description of the principles used in theinvention. `For this-purpose the axes of all the cylinders, as well as the counecting-pipe's, are thrown into one plane. The cylinders may be drferently arranged. They `may all except F F' have the same'axis and piston-rod 3 orthahot-air cylinders() C', D D', and F F' may be grouped about the furnaces, so asto e'conomize heat and room. An upright position of the cylinders would make. the pistons wear more evenly. v

Instead of cylindrical valves, slide or pup' pet valves may be used, andnearly all may be automatically worked. The pipes c o' should cuter the furnaces B B below the fire-grate and near the bottom, and the pipe j' should open ,near the top, as..shown by the dotted lines in Fig. 3. Instead ofthe use of soft and` unctu'ous rings of mineral substances, as described. the substances maybe supplied inthe state of powder oroth'erwise; and by varying the length of the strokes of the different pistons the cylinder may be made of different lengths and diameters, so long as the pressure on "G1 'and H or G and H' in opposite directions prejudicial to thel Working of the engine is counterbalanced substantially as described.'

What the inventor claims, and desires to ysecure by Letters Patent, is-

1.l Introducing cold air between two or mcre connected pistons or surfaces, so arranged that while between such surfaces it shall not materially increase in bulk, and heating it after it has been introdncedsandwhile .couiinedbetween such pistons or surfaces, and after the air so confined has been heated using the expansive force thereof for producing power by means and devices substantially as described.

2.' Arranging the said pistons or surfaces so that the pressure'of the heated confined air in opposite directions shall be balanced and neutralized, substantially as described.

3. The combination of the three cylinders and pistons, AA', GC', D D', and H H', or

their equivalents, substantially as described,

for the purposes set forth.

It.'v The arrangement ofthe furnaces betweenV the cylinders A A' and C G' or D D', substantially as described, for heatingthe air.,

5. Using soft lnctuous substances, substanftially as described, forlubricatng the pistons.

6. The arrangement of the valves or stopcocks, as d d d", for the purpose of cutting off one of the furnaces, so that fuel may be supplied without stopping the engine, substantially as described.

7. The arrangement of valves, operating substantially as the valves Nfl" in u and u', respectively, for the purpose of opening and closing the pipes between said cylinders and allowing the exit 'and escape of the hot air, substantially as described.

8. The. arrangement'of Yalves, as ss', for

vpreventing a partial vacuum when the air is not sufficiently7 heated to fillthe working-cylinder or its equivalent.

' COLLINS STEVENS.

Witnesses GEO. M. STEVENS, F. E. EMERSON. 

